Respiratory mechanics of Pekin ducks under four conditions: pressure breathing, anesthesia, paralysis or breathing CO2-enriched gas.
Impedance magnitude (Z) of the lower respiratory system was studied in Pekin ducks, using forced oscillations of a small volume at the airways opening in the range 1.6-16 Hz. The experiments were performed on 5 awake ducks enclosed in a body plethysmograph and spontaneously breathing ambient air at a transrespiratory pressure (Prs, the pressure difference between the lung and the body surface) which was varied in steps from -10 cm H2O (compression) to +10 cm H2O (distension). In 3 anesthetized birds, the effects of CO2 breathing and muscular paralysis were also studied. Analysis of end-expiratory Z data yielded estimates of respiratory resistance (R), inertance (I) and compliance (C). During positive or negative pressure breathing in conscious ducks, minute volume (V) and end-tidal CO2 (PETCO2) remained unchanged from normal (Prs = zero) while tidal volume (VT) and ventilatory period (Ttot) decreased. The respiratory system in late expiration can be modelled well with a simple series R-I-C mechanical model at Prs values of zero, +10 and -10 cm H2O. The value of Z increased at all frequencies studied during compression of the respiratory system (Prs = -10 cm H2O) and did not change much from normal (Prs = zero) during distension (Prs = +10 cm H2O). Both resistance and inertance increased during compression. During distension contradictory changes in resistance and inertance suggest that complex changes in flow profile and/or in flow pathways occurred with positive pressure breathing. Anesthesia or paralysis did not noticeably change the oscillatory resistance or inertance, but increased oscillatory compliance. CO2-breathing did not affect the respiratory impedance in late expiration, but reduced its flow dependence along the ventilatory cycle.
D000403:Airway Resistance; D000768:Anesthesia, General; D000818:Animals; D001696:Biomechanical Phenomena; D002245:Carbon Dioxide / Q000494:pharmacology*; D004372:Ducks / Q000502:physiology*; D008170:Lung Compliance; D008297:Male; D010243:Paralysis / Q000503:physiopathology*; D011175:Positive-Pressure Respiration; D012119:Respiration / Q000187:drug effects*
D002245:Carbon Dioxide